Recently, just got my power meter (Powerbeat G3) one sided.
I started zwifting using zpower, from 208 FTP to 253 FTP (not doing FTP test but climbing Alpe Du Zwift only). Then when I got my power meter, followed every instruction. Also calibrated before every ride and in some races after my warm-up. Also emailed the company of power meter because the starting setting is offset to -10% which I switched immedietly to 0 offset.
First race got 285 FTP and still able to sprint at the end, won the race. Next group ride it rose to 305 FTP because I chased hard the break.
Wondering if that would be true (accurate), because from 255 (zpower), my ftp now in power meter is 305. I also tend to tighten a little bit more my rear wheel when using zpower because I want to train harder before getting my power meter but the jump on ftp is big.
P.S. I did my 285/305 FTP race/rise hitting 193 max HR which I think would support the effort.